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Glossary-6 Acutime 2000 Synchronization Kit User Guide
Glossary
GDOP Geometric Dilution of Precision. GDOP describes how
much an uncertainty in pseudo-range and time affects the
uncertainty in a position solution. GDOP depends on where
the satellites are relative to the GPS receiver and on GPS
clock offsets.
geodetic datum A mathematical model designed to best fit part or all of the
geoid. It is defined by an ellipsoid and the relationship
between the ellipsoid and a point on the topographic surface
established as the origin of datum. This relationship can be
defined by six quantities, generally (but not necessarily) the
geodetic latitude, longitude, and the height of the origin, the
two components of the deflection of the vertical at the
origin, and the geodetic azimuth of a line from the origin to
some other point. The GPS uses WGS-84.
geoid The actual physical shape of the earth which is hard to
describe mathematically because of the local surface
irregularities and sea-land variations. In geodetic terms it is
the particular equipotential surface which coincides with
mean sea level, and which may be imagined to extend
through the continents. This surface is everywhere
perpendicular to the force of gravity.
GPD GPS with differential corrections applied.